I think there are lot of things that could be attached to that. Basically, “social techs” should be essentially flavor names, be it rituals or ceremonies in the religious or social fields. @lotus253 gave a number of hints on what was missing in DoM here (see notably the part with the big bold RITUALS).
If we just take into consideration such a social tech as “memory of the dead”: in a Ice Age family/tribe with 5 or 10 people, just speaking about a dear dead one is enough – basically like when in our family we speak about someone disappeared, telling stories about his/her life, his/her funny obsessions, etc. This is a way to create a cohesive link inside a small group like a family.
This obviously can’t work with a 200 people settlement, so to reach such a cohesive effect you need a proper ritual for the dead: a religious ceremony where every member gathers, a common sacrifice for the ancestors, a banquet and feast. This way, you could for instance have a higher cap for 30 more people in your settlement, and whenever you get this tech a dead cult may happen for instance once a year (or every 10 years, depending on timing in game). With an obvious price to pay for the banquet (food, etc.). And I may hear Lotus from here: “And shiny animations!!!”
There are lot of similar things that may be added as “social tech”: a cultic festival for harvest, for the moon, etc. Lotus could give a very long list if asked to, I’m sure of that.
Thinking about the political/social field, we could add the possibility for the big man (i.e. the player) to offer a banquet, to “buy” some important people or group or people with gifts to reassert his/her authority by showing his/her power and wealth, etc. That’s a very common practice, even today, called “paternalism” in the 19th-20th centuries when the boss of the factory used that (and think of company trips and sport events nowadays).
The bad side of such a feature with “social techs” could be having a sudden cap appearing: I think I remember you told once techs should be meaningful. The trouble is if just because you get a tech you may have +50 citizens in your settlement. To make the feeling far less “mathematical” (a.k.a. “stupid” in daily language), I think using triggered events would be totally fine to make things more fluffy:
- if your citizen number is 10% above the cap: an event may fire up: e.g. a feud between two family heads, whatever the reason, that may create bits of chaos;
- if you citizen number is 20% above the cap, then another event may fires up alongside the first one: e.g. disorder due to different political considerations among the groups of citizens/families, etc.
- if you are 30% above the cap, then could be added a story about the question of sharing ressources between groups if you’re lacking them, then creating another feud, etc.
- another case: if you’ve got some migrants who want to settle in and you’re already above the cap or about to reach it, you could get severe debates among citizens on what should be the ruler position on that: as a player you may want the newcomers to settle in as they’re damn good potters and on the long term that would be nice for every citizen; but some of those citizens may just wonder how everyone may get fed with the limited ressources of the settlement. Hence: debates, once again, and decisions to make to avoid chaos or deal with it.
One important thing is that if implemented such events should appear randomly once reached a threshold, giving a sense of real life in the settlement.
As usual, I’m not sure if this may help making my ideas clearer or easier to grasp. And probably you’re wondering how such a things could be done technically, while I’m just thinking on a theorical level. Don’t hesitate to say if that’s the case 